Identifying low melting point alloys.

I have been toying with the idea of doing some small-ish castings recently.
I have built my furnace (charcoal fired), which worked surprisingly
well for melting some aluminium scrap.
And I have found a cheap source of low melting point (unknown) alloys.
I live about five miles from a vehicle crime "blackspot" and there is usually at least one newly burnt out car every day whilst walking the dog. When these cars are removed, there are usually "puddles" of alloy left behind - sometimes obviously the remains of alloy wheels, but often just melted components.
Over the last three months, I've managed to collect about 100lbs of these.
I have some bits which are obviously lead, and some which are obviously aluminium, and quite a lot (say 90%) which are not obviously either.
I'm not doing any critical castings - mainly ornamental.
I have no way of controlling or measuring the temperature in my furnace.
Is there any (cheap) way of identifying what the alloys are? Will it cause any huge problems if I just melt all the lot together?
--
BigEgg


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 30 Oct 2005 21:55:16 +0000, bigegg

Sounds like Mazak - a zinc alloy intermediate in density and strength between lead and aluminium alloys. Use a saturated solution of copper sulphate acidified with a few drops of battery acid. Lead and aluminium alloys will be unaffected but zinc alloys will turn dense black. Some magnesium alloys will also darken but not as much as zinc alloys. Mazak is a useful casting alloy in it's owm right but keep it well away from aluminium alloy - even a small inclusion is injurious.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mixing metals without knowing their composition will most often result in useless stuff. Also some mixes will produce poisonous fumes - e.g. Antimony (in babbitt metal) and Aluminium. Also the very low melt alloys often contain Cadmium, which is a big no-no if you overheat and gas it off - which you are sure to do if you try to mix with a higher melting point metal.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Phil wrote:

Useless in what way? Crumbly?

A mixture of babbit metal and aluminium gives off poisonous fumes? or some mixtures of babbit metal give off fumes?

Luckily, by the time it's been in a burnt-out car, I doubt there is much cadmium left, but I'll bear it in mind.
I think I'll stick to the remains of alloy wheels in light of the above, and discard all the small, unkown pieces.
Should still leave me 20 or 30lbs of usable stuff
Thanks!
--
BigEgg


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Crumbly it can be. Many non ferrous alloys are very sensitive to impurities which can weaken their crystal structure. Either immediately, or over time in a form of intergranular corrosion. Zinc alloys for example are badly affected by small qauntities of Iron or Lead. Tin alloys pour like porridge if you put a high proportion of zinc with them, and can have a brittle crystal structure if you put more than about 4% zinc. None of it matters a lot if you are just producing doorstops - except they may be unsightly due to porosity and become brittle with age.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Rather than gambling on alloys of unknown quality, you might find your local refuse tip to be a better source of raw materials. Most tips ( or rather, Recycling Centres ) separate out dumped metals into separate bins, and a bag-load of clean alloy will only cost a pound or two.
You might even come across the odd handy tool - such as a set of Clarkson Autolock collets, in a somewhat disheveled state, seen at my local tip yesterday.
Regards,
--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stephen Howard wrote:

Agreed, this is a good tip(no pun intended). I got an old extended-opening 4" bench vice for 50p this way, and just missed out on a petrol engined strimmer for 1.
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Peter Neill wrote:

Not around here I won't
Big signs up saying "people taking stuff from the skips will be prosecuted"
or words to that effect.
--
BigEgg

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

There's a difference between taking and buying. Most tips these days are operated by private sub-contractors who have 'totting' or salvage rights. These rights are nearly always taken into account when they quote a price for servicing the council's amenity, and sales from salvage can account for a significant proportion of the site's profitability.
And I can fully sympathise with them having to put up such notices - at the prices they tend to charge for items it's hardly worth stealing the things. In effect, it's like nicking the waiter's tip off a table in a restaurant. I've bought 2+Ghz computers for less than a tenner, any number of useful ( and otherwise expensive ) leads and PSUs for a couple of quid a throw - even a Bosch dishwasher and a four stroke mower for a fiver a-piece. It used to be the case that people chucked stuff away when it was knackered, but these days it seems that just 'fancying a change' is enough to consign fully working items to a hole in the ground.
Most places have a little spot where items for sale are kept, but on the whole pretty much everything should be available at a price if you just ask. If they seem reluctant, make them an offer - it's often the case that they don't know the worth of an item ( particularly old engineering items ), and that's how I picked up a Blue Macs cast iron bench press for a fiver. I even picked up a gunsight for a Vickers .303 machine gun for a fiver...got 40+ on ebay for it!
If you don't have any luck, try the tip in the next town!
Regards,
--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stephen Howard wrote:

I had a word - the employees are under threat of dismissal for taking stuff. It all goes in big skips, straight to a landfill or scrapyard

This is Leeds, Wakefield and Bradford are the two other nearest, and they are under the same regime.
Believe me, I tried.
--
BigEgg


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

My experience matches Stephen Howard's. But not the profit bit 8-(. Looks like I'd better not hint where I go scavenging.
-- cerberus
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.